1. Field of the Invention
The present invention relates to clamping collars and is applicable notably to the field of the automotive industry, for example for coupling and clamping the various component elements of an exhaust pipe and muffler system.
The usual function of a clamping collar is to exert a tangential stress on the member about which it is disposed in order to cause a shrinkage of its diametral dimensions and consequently a clamping action.
2. The Prior Art
Various clamping collar types have already been proposed, their design and mode of operation being consistent with the specific use for which they are intended. More particularly, if in addition to their clamping function they must provide a reliable fluid-tightness, they must also have certain well-defined properties.
Regarding the specific domain of clamping collars intended for attaching and coupling the various component elements of the exhaust system of motor cars, nowadays these devices consist mainly of a split ring having its ends assembled by a clamping bolt. The split ring is cut and pressed from a metal sheet blank so that it can withstand the relatively high temperatures developed in actual service.
An exhaust pipe system comprises a plurality of interfitting pipe sections providing an adequate fluid-tightness at the joints. The first pipe section at the engine end of the system is split so that its diameter can undergo a certain degree of distortion when the collar disposed around the outer periphery of the coupling is tightened.
This arrangement was acknowledged as satisfactory at the first onset, though the resultant fluid-tightness is far from perfect; moreover, the clamping collar may be of very simple design.
However, exhaust system component elements are exposed to oxidizing factors reducing their useful life at a rate increasing with the temperature developed by the engine. Moreover, these exhaust components are usually disposed under the vehicle floor and therefore exposed to all kind of splashes so that after a relatively short time it is impossible to disassembled the pipe sections from one another. This seizing of the exhaust system elements constitutes a serious trouble since in many cases only one part of the system must be replaced and this impossibility of disassembling the parts is such that the complete exhaust system must be replaced unnecessarily. Obviously, the final cost of this operation is high and the car owner is not pleased.
In an attempt to solve this problem, some manufacturers have used and still use the so-called biconical fitting method. In this case, one end of the pipe to be connected is outflared and the adjacent end of the other pipe to be connected has an externally bevelled contact surace engageable by the outflared edge of the first pipe. The joint is consolidated by means of a collar having an internal V-sectioned groove encircling the two pipe ends.
However, this collar must necessarily be split into two halves so that the assembling thereof is more difficult than with conventional collars. Moreover, the manufacture of collars of this type is more complicated and consequently more expensive.
Though satisfactory from the technical point of view, this arrangement is awkward to use, and furthermore it is expensive and therefore not likely to be widely accepted in the automotive field.
The use of plain tubular pipes assembled in end to end relationship is more satisfactory since in this case the pipe manufacture is simplified and therefore more economical. On the other hand, the clamping collar must be such that it will not only provide the necessary mechanical coupling of the two pipe ends but also the fluid-tightness of the coupling joint.